Responses to Peer Reviewers' Comments on the Proposed Revision to the Radon Guideline

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Health Canada has proposed that the current guideline for exposure to radon gas be reduced from 800 to 200 becquerels per cubic metre (Bq/m³). The Federal Provincial Territorial Radiation Protection Committee (FPTRPC) appointed a Radon Working Group to review this recommendation and report back on its findings. This review was completed in the fall of 2005 and supported Health Canada's proposal.

The FPTRPC requested that a draft revision to the Canadian radon guideline and the associated Working Group report be made available for public consultation, including a peer review by eminent scientists. The purpose of the peer review was to solicit comments on the scientific basis for the proposed change to the guideline and the approach used for its development. This review was conducted from April 24, 2006 to June 22, 2006 inclusive, along with the public consultation.

The peer review consisted of five eminent scientists; three from Canada, one from the U.S. and one from the U.K. Responses to their comments are summarized below. In order to provide anonymity, their names and affiliations were removed from their comments.

Reviewer No. 1

A. General Comments

I am in general agreement with the proposed guideline especially in view of the recent pooled residential case control studies.

I suggest however, that Health Canada needs to be cautious in their use of terms like "national program", "mandatory", "required" , etc.

B. Recommendations

The proposed new radon guideline of "200 Bq/m³ in the normal occupancy area" is, in my view, both quite reasonable and timely, given the findings from the recent North American and European pooled residential case-control radon studies.

I am not certain, however, of the intent of the guideline, for example, is the intent to require people to undertake remedial action when the long-term radon levels in normal occupancy areas are above 200 Bq/m³, or rather, is the intent that people be educated about the hazards arising from exposure to radon at levels above the proposed criteria in order to make an informed decision about remedial actions? If "required" who pays, the Federal Government, the Provinces, the homeowner?

I agree with the concept that the higher the radon level is, the more expeditiously remedial action be carried out but as noted below, suggest that the document provide additional discussion about the basis for assigning priority.

I also agree with the concept that radon control measures be considered for new construction, especially, in light of the anticipated efforts for increased energy efficiency some of which may have potential to contribute to both higher levels of indoor radon per se and higher equilibrium factor.

C. Specific Comments

Points of clarification

#3 As indicated above, this section suggests that immediate action is required for radon levels above 800 Bq/m³. As before, does the "guideline" actually intend "to require" or rather "recommend"? (and similar other statements)

I suggest that the time-frame for remediation be qualified in some way. I agree that exposure to "a radon concentration of 800 Bq/m³ exceeds the guideline value by 600 Bq/m³ and that after one year, this represents a cumulative excess exposure of 600 Bq years/m³". However, I suggest that some further discussion (context?) be provided as to why this might be a reasonable approach to assigning remediation priority be given. Consider, for example, exposure at 200 Bq/m³ for 35 years which represents 7000 Bq years/m³. One year at 800 represents a little over 10% of this, 2 years 20%, etc.

Rationale

#1 Perhaps semantics, but I believe that it would be difficult to measure incremental risk at 100 Bq/m³. For example, consider Figure B2 which shows the dose-response relation for the North American pooled study. The 95% CIs at all levels of exposure include "0". There is, however, a highly statistically significant excess risk based on the North American (and very importantly, the European) pooled residential case control studies. I suggest that a rewording be considered here.

#3 Do we really know that non-smokers would in fact be willing to spend money to carry out remedial action?

I agree that below about 200 Bq/m³ that it becomes increasingly difficult to separate the radon contribution to background dose.

Introduction

Para 1, line 5, again I think that Health Canada should consider rewording of "measurable" to something like "statistically significant".

International Approaches to setting Radon Guidelines

Para 2, it might be helpful to provide some clarification as to what is meant by an enforceable standard (Switzerland) and how that is different from what Health Canada is proposing.

3.2 Recent Evidence from the combined, etc.

2nd para, line 6, in reference to European pooling. I think the adjustment by Darby et al. is for exposure correction rather than outliers (at least by my understanding of the word outlier).

3.3 Individuals

This section summarizes risks to smokers and non-smokers. I suggest that the basis for these calculations be provided. For example, is Health Canada using the Krewski et al (North American pooling) relative risk estimates or those of Darby et al. (European pooling)?

The source of the underlying risks of lung cancer should also be identified. (e.g., What is the source of baseline risks to non-smokers and to smokers; Did Health Canada use average of rates in men and women? Etc.)

3.4 Population risks

1st para following Table 3.4, reference is made to Stats Canada 1997, presumably for mixed population of males and females as existed at the time. (Does Health Canada have smoking prevalence data for this population?)

The method of estimating lung cancer risk is from U.S. EPA which is a modification of BEIR VI and based on miners data. While the miner data provide a strong basis for risk assessment, the EPA methodology is not necessarily the best method for estimating risks. As a minimum, the report should acknowledge that the miner data form the basis for the estimates in table 3.4.

4. Radon testing

4.2 I recognize that at present, that radon data are a bit scarce for a Canadian map and support Health Canada in their efforts to develop a national radon map. It will be important, however, for Health Canada to consider (at very least to acknowledge the data limitations) the relative quality of the various data that they currently are using and plan to use.

5. Radon mitigation

Would it be appropriate to reference the U.S. EPA Website here?

I suggest that Health Canada should reference the source of the cost data for the radon remediation actions, otherwise, it gives the impression that Health Canada has developed this data itself. (In such event, the Health Canada source should be referenced.)

6. Cost Estimate

A logical question would be whether Health Canada or the provincial governments will pay for the testing? (As I read the wording of Section 6.8, the use of the term "national program" implies some federal obligations. I think the document needs to be careful in use of "national program", "required" etc.)

Has anyone looked at potential effects on property values?, Have Health Canada or the provinces had preliminary consultations with Real Estate Boards or housing developers, etc., in the various provinces?

7. Implementation

In my view, the key issue is public education (7.2).

Does Health Canada (can Health Canada) make radon testing mandatory in real estate transaction? Is this the intent? Is this necessary?

Reviewer No. 2

Summary

The subject document has been reviewed, along with a number of the referenced documents, in particular Darby et al. (2004), Krewski et al. (2005), and Lubin et al. (1995), I found the Darby and Krewski papers to make the best case that I have yet seen for implicating indoor radon as a risk factor for lung cancer in the general population. However, I do not think that the Radon Working Group has done a good job of presenting its case for the specific radon guideline that it is recommending. There is insufficient information on the basis for and methods of calculation used to reach some of the conclusions. I would also argue that life saving is not the issue. Since all will die, the only thing that man can control is the cause and, hence, to some extent the timing of death. Therefore, the case has to be made in terms of years of life lost or preserved. I would also question the special treatment recommended by including schools and hospitals in the definition of dwellings. This is more a matter of political correctness than a scientifically defensible recommendation.

In the absence of further information, I would agree that a reduction in the Canadian radon guideline is justified. I would suggest a two-tier recommendation with 400 Bq/m³ for existing houses and 200 Bq/m³ for new construction, but only after a cost-benefit analysis based on years of life saved.

Detailed Comments (referenced by page number and section heading)

Page iv, Rationale 1. Recent scientific evidence...

I would suggest a slightly more conservative statement than "measurable risk of lung cancer at radon levels as low as 100 Bq/m³". Darby et al. had twice as many cases and nearly three times as many controls as Krewski et al. but limited their conclusion to "the dose-response seemed linear with no evidence of a threshold, and a significant relation remained ...below 200 Bq/m³". While the trend is clear in both studies, even at 200 Bq/m³ the lower confidence limits on the relative risk are below 1.0. The preponderance of cases (and controls) in both studies is in the region below 100 Bq/m³ where it is becoming increasingly difficult to distinguish from background. Therefore, I recommend that Darby's wording be used.

Page iv, Rationale 2. Harmonization...

While harmonization with international guidelines and practices may be a good ideal, it may not always be practical. When I look at the list of countries in Figure 2.0, I am reminded of a criticism that is often leveled at Canadians - that we are profligate users of energy. A major reason for that is our climate. We require better sealing of our houses, with heating systems in use longer than almost all of the countries in the table. Even the Scandinavian countries are warmer than Canada because the warm Gulf Stream curls north and east after it passes the British Isles. The three countries with the highest radon guidelines are Switzerland, Canada and Russia. Russia has a similar climate to Canada. I have no data at hand on Switzerland, but because of its high elevation, it may have similar heating requirements. For the rest of the countries, a lower radon guideline does not represent nearly as much of an economic burden as it does for Canada. Since we do not have an infinite supply of money, we must do cost-benefit analysis to determine how best to spend our money for health benefits. Hence, citing international harmonization without cost considerations cannot be used as a justification for the radon guideline.

Page v, Rationale 3. Balance between risks...

It is incorrect, and in fact misleading, to speak of saving lives (by preventing lung cancer). We shall all die. We can only influence the cause of death and, as a result, the time of death. It would be much more appropriate to speak of years of life preserved. I do not have the reference at hand but I recall a document written by Sir EE Pochin for the International Commission on Radiological Protection (ICRP) on cost-benefit analysis, which addressed this very topic. Lung cancer is a disease of middle and old age. The mean years of life lost due to lung cancer are probably about 15. In contrast, accidents are randomly distributed through life and, in fact, are a principal cause of death for those in their teens and 20s. My recollection is that Pochin concluded accidents to represent a mean loss of about 35 years of life. On that basis, if costs were equal (accident prevention versus radon reduction), it would be far more cost-effective to spend money on reducing accidents than on radon concentration reduction. Before recommending any change to the Canadian radon guideline, I would strongly recommend a cost-benefit analysis on years of life saved by various actions that could be mandated by federal or provincial governments.

Page 1, 1. Introduction

Please refer to the comments above on Rationale 1.

Page 1, 2. International Approaches to...

I question the propriety of citing draft documents of the International Commission on Radiological Protection (ICRP). In recent years the ICRP has floated many radical proposals that have not come to fruition after international review. The revised recommendations are still subject to change and cannot be used as a justification for revising Canadian requirements.

Here and in following sections equivalencies are cited between radon concentrations (in Bq/m³) and radon progeny concentrations (in working
levels - WL), exposures (in working level months - WLM) and effective doses in millisieverts (mSv). These transformations are critically dependent upon several assumptions. To convert radon concentration to WL, one must define the equilibrium factor between radon and its short-lived progeny (generally in the range of 0.3 to 0.5, but more extreme conditions do occur). To further calculate exposure (WLM) requires an assumption of occupancy factor (how many hours per day or per year is the person exposed in these conditions). The conversion of exposure in WLM to effective dose in mSv is a further complication. It has been shown that the ICRP lung model overestimates the effective dose by factor of three. The ICRP has circumvented this difficulty by adopting a dose conversion factor of 5 mSv per WLM. In making the conversions here and in following sections, the authors should clearly state the equilibrium factor, occupancy factor and dose conversion factor being used.

Page 2 text and Figure 2.0

Please refer to the previous comments regarding harmonization.

It is also noted that a number of countries have separate guidelines for existing and new dwellings. It would be foolish indeed to force an elderly couple, who have lived in a house for 40 years, to spend money on radon reduction. On the other hand, if "radon proofing" can be accomplished in new construction at minimal expense, then it would be foolish to ignore this option. I would strongly support a two-tier recommendation. I would suggest reducing the current guideline from 800 to 400 Bq/m³ for existing houses and setting an objective of 200 Bq/m³ for new construction, but this should only be done after a cost-benefit analysis based on years of life saved.

Page 3, Table 2.0

The equivalence between Bq/m³ and WLM/year is critically dependent upon the assumptions made regarding equilibrium between radon and progeny and occupancy factor in the residence. These assumptions should be specified. I can equate the 800 Bq/m³ and 4 WLM/y shown for Canada with assumptions of F = 0.5 and occupancy of 72%. Is there some justification for these assumptions? I must also ask if there is some documented evidence for the rationale for 800 Bq/m³ being equivalent to 4 WLM/y, the limit for uranium miners.

Page 4, 3.1 Earlier evidence...

The fourth sentence incorrectly implies that the National Cancer Institute has issued some statement concerning lung cancers in miners. The reference is to a paper published in the Journal of the National Cancer Institute. This paper represents the opinion of the authors, not a statement by the Institute itself.

Page 4, 3.2, last sentence

Typo: Appendix B, not A

Page 5, 3.3 Individual risks

It is not clear how the lifetime lung cancer risks of radon exposure for smokers and non-smokers have been calculated, nor what data were used as the basis for the calculations.

Page 6, 3.4 Population risks

Some details should be shown on how the referenced data were used to arrive at the estimated number of lung cancers attributable to radon. As a crude example, the weighted mean of the geometric mean radon concentrations in the 13 cities reported in McGregor et al. is 0.384 pCi/L, which is less than the U.S. EPA outdoor radon concentration (0.4 pCi/L). On this basis, there should be no attributable lung cancers. In contrast, Jalbert reported that the average indoor radon concentration in American homes was 1.25 pCi/L. It further should be noted that the cross-Canada radon survey reported by McGregor et al. was conducted during the months of June, July and August, when radon concentrations are likely to be near the annual low point but sampling was done in basements where possible, which is likely to bias the results toward the high side. How these opposing factors were taken into account in the calculations should also be discussed.

Page 8, first paragraph, line 3

Grammar: The number of tracks is...

Second paragraph, last line

Typo: success of a radon reduction program.

Page 9, 5.1 Pathways for radon entry into homes, last bullet point

Typo: pores in the faces of blocks

Page 10, second paragraph

A further item could be added to this paragraph on closure of soil gas entry routes: Floor drains connected to weeping tile systems should be fitted with a trap and a water supply to ensure that there is always water in the trap to act as a radon barrier.

Fourth paragraph, line 1

Typo: ...radon in well water...

Fifth paragraph, line 1

Typo: The cost...ranges from...

Pages 9-11, Sections 5.2 and 5.3 General comment

It would be worth emphasizing the quality of seal required to prevent the ingress of radon, possibly by reference to the CMHC/Health Canada guide (Radon: A Guide for Canadian Homeowners). I mention this because I have seen a contractor attempting to seal openings in a floor slab by standard construction techniques that are insufficient to seal out radon.

Page 12, 6. Cost Estimate..., first paragraph

I would dispute the suggestion of vulnerable populations in schools and hospitals. The BEIR VI Committee considered vulnerability of different age groups. They mentioned infants as having a slightly higher risk because their higher breathing rate could result in greater dose to the lungs from a given radon concentration; however, in the final model they ignored this effect because it made a small contribution to overall risk. School-age children are not infants and should have no greater vulnerability than other members of the general population. A better case could be made for considering day-care centers, which look after much younger children. In any event, children spend perhaps 30 hours per week in school, making school exposure much less significant than home exposure.

However, it should be mentioned that some ecological studies have shown a positive correlation between indoor radon and some childhood leukemias. The most recent study shows a positive association between indoor radon and the incidence of acute myeloid leukemia in French children under the age of 15.

With respect to hospitals, with the exception of one or two very rare inherited conditions, I know of no evidence that a person suffering from any other disease is more vulnerable to cancer induction due to radiation exposure. Most hospital patients are only in hospital for a short time, making the hospital a very small component of their overall radon exposure. For persons in long-term hospital care, the disease that has resulted in their hospitalization is more likely to contribute to their demise than lung cancer.

For both schools and hospitals, the staffs would be at higher risk than the students and patients because the staff are present in the buildings for a much greater fraction of time. However, this is not different from any other workplaces. If the intent is to include all workplaces in the guideline, then this can be done without invoking questionable vulnerable populations.

Page 12, 6.1 paragraph 2

The 2.67% of houses above 200 Bq/m³ does not appear to be derivable from the data given in McGregor et al. Have the authors of this document gone back to the actual raw data from the surveys reported by McGregor et al. to derive some of their conclusions? If so, it would be helpful to include the additional information that is not available in the published paper.

Page 18, 6.8 Conclusions

The development and use of a radon potential map would be a useful contribution to this work and could reduce testing costs by focusing work on areas of higher radon potential. However, the reduction in radon testing costs suggested as a result of economies of scale is probably overly optimistic. The American program has been in force for many years and has resulted in millions of tests but Jalbert notes that do-it-yourself test kits still range from U.S.$10 to U.S.$50 and professional testing ranges from U.S.$75 to U.S.$350.

Page 19, 7.1 Initiation of...

The process of adopting the new guideline omits the possibility of revising the guideline after the 60-day comment period.

Page 19, 7.2 Public Education

Second line, Typo: Aspects of...

The not-insignificant costs of the proposed public education program have not been considered.

Page 20, 7.3 Building an Infrastructure...

Calibration facilities, standards and a certification program for radon testing will all be needed. Also, the suggested construction standards and building code revisions will be needed. Again, these represent additional costs that have not been considered.

Pages 20-21, 7.6 Financial Support...

This section is advocating spending public money on a risk-aversion or health-promotion strategy. No effort has been made to demonstrate that this would be an optimum use of public funds. In terms of dollars per year of life preserved, there may well be many other strategies that are more effective.

Page 26, 2. Consistency, 6^th line

Typo: I suspect the superscript 4 should have been reference 10.

I am not sure why the Shenyang study is the only study mentioned, specifically with negative results. There have been many residential radon studies that failed to show a correlation between radon in homes and lung cancer.

Page 27, 3. Specificity

I question the statement that lung cancer is the only known health effect of radon. As mentioned previously, radon has been implicated in other childhood leukemias. I also recall that Dr. J. R. Johnson has been examining the relationship between radon exposure and cardiovascular disease.

Page 27-28, 7. Coherence

It is not clear how the "risk equivalent dose" was arrived at.

As noted previously, the work of Burchall and James has shown that the ICRP lung model consistently overestimates the risk of lung cancer from radon. This could arise from either the radiation weighting factor for alpha particles or the dose and dose rate effectiveness factor, or even a combination of the two.

Page 28, 8. Experimental intervention

I would have to concur that it is most unlikely that implementation of the radon program would result in any demonstrable reduction in lung cancer rates.

Page 28, 9. Analogy

I do not think the analogy factor has been correctly handled here. There is no doubt that high exposures to radon (or more correctly radon progeny) can cause lung cancer. What is at issue is whether low radon concentrations, only slightly above outdoor air concentrations, can cause lung cancer. The radium analogy fails because high radium intakes by the dial painters had clearly resulted in bone cancers, whereas lower radium intakes demonstrated a threshold below which no cancers occurred. I would refer the reader to the extensive work of Dr. Robley Evans on this subject.

Page 28, last paragraph

It is not correct to state that "nearly all of Hill's nine criteria" have been satisfied. Criteria 3, 8 and 9 fail and 1 and 2 are only satisfied by the combined studies.

Reviewer No.3

In general it seems to me clear and sensible. I have a few points of detail:

1. In figure 2.0, Switzerland is shown as having a guideline of 400 Bq/m³ for new buildings and 1000 for existing buildings. In fact they have two guidelines that both apply to existing and new buildings: 400 Bq/m³ is a guideline for inexpensive remedial measures, and 1000 Bq/m³ is a compulsory limit.

2. On page 4, para 3, it is stated: "If their radon measurements are statistically adjusted for the effects of high outliers, then the odds ratio increases to 1.16 " The adjustment is in fact for the effects of year-to-year variations in radon levels in houses, not for high outliers.

3. On page 7, radon measurement techniques are discussed. The discussion puts the emphasis on short-term measurement methods, which are the least accurate. I would suggest reversing the emphasis, and suggesting long-term measurements except in cases where that is not feasible.

Reviewer No. 4

You will find below few comments concerning the, "Report of the Radon Working Group on a New Radon Guideline for Canada". Except for the first comment, no change to the new guideline is proposed. Other comments should then be considered as suggestions to improve some aspects of the document.

Although I agree that the higher the radon concentration, the sooner remedial measures should be undertaken, I'm not sure if I would recommend the calculation of a time frame for action, such as proposed in the document. Although scientifically correct, I fear that such an approach could be used as an excuse for inaction. At 250 Bq/m³, the calculated action time frame would be 12 years which is a very long time, even when housing is concerned. Conversely, one could argue that at 2400 Bq/m³ , the calculated time-frame being 3 months, urgent action is needed. Some people might then be pressured into unreasonable (very high cost) remedial measures by unscrupulous entrepreneurs. A simpler recommendation would be better understood and would lead to less undesirable effects. For example:

Remedial measures should be completed within 1 year, especially if the radon concentration is above 800 Bq/m³. If radon concentration is considerably above 800 bq/m3, don't delay remedial measures.

It might even be simpler not to talk about a time frame for action.

I'm assuming that the health impact of radon is calculated, using the current smoking rate in the Canadian population. It would have been a good thing to have a more detailed description of the tobacco impact on radon health risk. A good understanding of its impact is important for decision-makers. The document could have included the proportion of cancer caused by radon that is also related to smoking and the impact of declining smoking rates on radon health impact.

Although the number of deaths caused by radon (Table 3.4) is based on appropriate calculation, this number is considerably above the number of preventable deaths related to radon, if the 200 Bq/m³ guideline is applied. Most deaths related to radon will occur in people exposed to low levels of radon, levels below the proposed guideline. This concept is important because it is the scientific basis for proposing universal (or very widespread) radon proofing of new homes. Radon proofing of new homes should lower the exposure in homes that would have never tested above the guideline. Since these homes are much more numerous than those above the guideline, the health impact in the long term of universal radon-proofing could be important. Consequently, I'm not sure that radon proofing should be limited to high radon area, unless one is confident that the radon levels in a specified area are generally close to outdoor levels.

The concept of radon potential map is interesting, if it is part of an approach where it is widely used. It can be used for setting priority, but it must be used with great care. Map resolution is important as small areas with high levels of radon could be hidden in a large area with average radon levels. The cut-off levels (between low, average, high radon potential, etc.) are also important as they might greatly affect the number of homes prioritized or not. If universal radon testing is proposed (without setting priority), at best, a radon potential map would be of little value and at worst, it could be used as an excuse not to test. Some might find it useful to identify areas with very high radon levels if the map resolution allows it.

It should be noted that the cost estimate in Section 6 does not include the implementation cost of a national radon program (Section 7). The cost of a national radon program should include more than the cost of tests and mitigation.

On page 20 (Section 7.5), it is overly optimistic to assume that the proposed measures could lead to complete compliance with the new guideline, no matter which time frame is considered. Conditions that could lead to 100% testing of homes are probably different than conditions that could lead to 100% remedial actions in homes with radon concentrations above the guideline, even if the efficacy of remediation is not taken into account. Let's not give decision-makers false hopes about this challenge. Radon will not be an easy health risk to control.

Reviewer No. 5

Thank you for the opportunity of commenting upon your proposed reduction in the radon action level for Canada; from 22pCi/L (800 Bq/m³) to 5pCi/L (200 Bq/m³). These are our final comments.

A. General Comments

1. You have proposed an action level of 200 Bq/m³ (~5 pCi/L). We strongly support Canada's move to a lower action level from your previously (relatively) high level of 800 Bq/m³ ( or 22 pCi/L). Your proposed action level for dwellings puts Canada more in line with the many other countries, especially for new dwellings (Figure 2.0). Also, we support your choice of a single action level applicable to new and existing dwellings, as does the U.S. and several other nations.

However, it is important to note that given the evidence for lung cancer risk at relatively low levels (e.g., Darby et al.), and the U.S. risk assessments (U.S. EPA, NAS) for about 21,000 radon related lung cancer deaths from residential (dwelling) long-term exposure to about 46 Bq/m³ (1.25 pCi/L), might Canada consider setting the action level at 148 Bq/m³ (~4 pCi/L)? Presuming that the average indoor radon level in Canadian homes is similar to that in the U.S. (46 Bq/m³, ~1.25 pCi/L), what with Canada's colder climate overall, might not Canadians have a similar risk given that they likely spend as much (or more) time in their homes (and in other buildings) as do Americans?

2. Remedial measures should be taken within one year at 800 Bq/m³ (22 pCi/L). Taking action to minimize a future lung cancer risk should always be preferred over delaying such an action. Taking action to reduce the level of radon (e.g., at 200 Bq/m³) will help reduce the future risk of lung cancer. So your recommendation to Canadians that they act sooner, the higher the radon level, is a good one. EPA's voluntary program has found through much research, experience, trial and error, that comparing the radon risk to other well known risks allows consumers to decide how urgently to reduce the radon level in their homes (e.g., see page 12 of the Citizen's Guide to Radon at http://www.epa.gov/radon/pubs/citguide.html); this same risk comparison table can be seen at http://www.epa.gov/radon/healthrisks.html.

3. Radon Documents and Protocols. The U.S. EPA would be pleased to provide Health Canada with master electronic editable copies of our available radon documents should Health Canada wish to adapt them for use with Canadian citizens.

B. Specific Comments

Page iv: You might also consider using the ALARA concept in item #4, i.e., As Low As Reasonably Achievable The detail behind the concept is easily found on the Web (e.g., http://www.nrc.gov/reading-rm/basic-ref/glossary/alara.html).

Page v: (Item #3 - Balance between risks regarded as too high to ignore and a practical value). "The relative risk for developing lung cancer for a non-smoker is doubled for a lifetime exposure at 200 Bq/m³ and is thought to represent a risk level at which non-smokers would be willing to take remedial action. As the radon concentration is lowered from 800 to 200 Bq/m³, the number of lives saved steadily increases and the cost-per-life-saved decreases. It is not clear that there would be any further increase in benefit below 200 Bq/m³ as the radon contribution to total dose begins to merge with the overall radiation background." [This level is about 10 times the average ambient (outdoor) radon, and about 4 times the average indoor levels. The major reasons for stopping at 200 Bq/m³ would be technological feasibility and/or cost considerations.]

Page 3 : In the United States, the selection of our action level (4 pCi/L) was selected (rationale) based on risk, mitigation technology and cost.

Page 7: (Radon Testing) Canada may want to consider/describe testing in homes in a more detailed way; particularly for residential real estate transfers or transactions. As you know, the U.S. protocol calls for two test devices (passive - e.g., charcoal based) or a single device (active - e.g., continuous radon monitor). The real estate protocol is spelled out in our Home Buyer's and Seller's Guide to Real Estate (http://www.epa.gov/radon/pubs/hmbyguid.html).

The new guideline may prompt more testing (and mitigation) at the time of real estate transfers, as it has in the U.S. Real estate drives the bulk of testing (>75%) and mitigation (>85%) in the U.S.. We found that a testing protocol unique to real estate was needed following the release of our updated Citizen's Guide in 1992. This was true for several reasons: (1) because of shorter time frames which do not accommodate a longer-term test - there simply wasn't time to take a screening measurement followed by a confirmatory measurement; (2) not enough time for a longer test; one of the two recommended approaches in the Citizen's Guide; (3) the need to make a mitigation decision quickly based on reliable results. You might also reconsider the page 20 reference to real estate with this in mind.

Page 11: This section and the References section should include more information about the fact that radon-resistant features are contained in Canada's National Building Code (first published in 1995).

Page 12: Section 6.1 - Radon Testing and Mitigation. Canada may want to distinguish between "one test" and "one test device" here. Again, this is related to real estate (see above). The U.S. real estate protocol, the real estate test is very often two test devices (passive).

At the end of 2005 in the U.S., there were approximately 630,000 homes w/an operating mitigation system (HOMS), i.e., an active working ASD system. Two years ago, we changed the measure for "homes mitigated", because a mitigated home does not remain "mitigated' indefinitely due to radon vent fan failure.

Page 15: Section 6.5 - New Home Construction with Radon-resistant Technologies. At the end of 2005 in the U.S., an estimated 1.4 million homes had been built to include radon-resistant features (since 1990).

Page 20: Section 7.5 - Radon Testing in Real Estate Transactions. To our knowledge, there is no mandatory radon testing in real estate transactions at any level of government in the U.S. (city, county, state, federal). Mandatory testing may be a matter of policy or practice for some private organizations, e.g., a company with an employee relocation program that tests the employee's "departure" home and possibly their "destination" home.